[qazibasit (OP)]

what is the difference between caffeine and theophyllin? Are they  the same thing ?

[Ylide]

Theophylline is structurally similar to caffeine.  They differ by a methyl group.  Both are found in black tea.  Coffee, I believe, contains only caffeine.  Theophylline is more commonly used in therapy for breathing disorders....not sure exactly why it's preferred.

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[gsmollin]

Theophylline is employed as a broncial dilator, to treat asthma. Caffeine does not have this side effect, although they are both stimulants.

[chris]

Theophyllin and caffeine are methylxanthines. They inhibit an enzyme called phosphodiesterase which normally removes a substance from the cell called cAMP (cyclic adenosine monophosphate). cAMP is known as a 'second messenger' and functions as the cellular equivalent of an errand boy, switching various processes on and off in the cell. By breaking it down, phosphodiesterase terminates its action and limits its effects. If the phosphodiesterase is prevented from working, by theophylline binding to it, then the cAMP hangs around in the cell for much longer and hence the various actions of the cAMP are increased.

One of the roles of cAMP is to relax smooth muscle, including that found in the walls of the airways (bronchi). So boosting the levels of cAMP can help the airway muscle to relax (dilate), relieving some of the bronchospasm that causes patients with chest diseases to wheeze.

Significantly, one of the substances that stimulates the production of cAMP in the first place is the stress-hormone adrenaline. That's why a few too many strong coffees can produce the symptoms of an adrenaline rush, leaving you trembly and agitated - because the caffeine in the coffee inhibits your phosphodiesterases, boosts the levels of cAMP in your cells and so potentiates the action of any adrenaline in your bloodstream.

Chris

"I never forget a face, but in your case I'll make an exception"
 - Groucho Marx

[Ylide]

So Chris, why the subtle differences in the effects of caffeine and theophylline?  They both cause bronchial smooth muscle relaxation due to  excess cAMP via the same phosphodiesterase inhibition pathway, right?  Then why is theophylline used more often therapeutically?  

Also, is this same smooth muscle relaxation why coffee and tea cause one to have more regular bowel movements?



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[chris]

I think that theophyllin is more potent than caffeine - it certainly has a narrowed therapeutic window (if my memory serves) compared with caffeine. I think that it is a more effective blockade of the enzyme, but don't quote me on that !

I'm surprised that you say caffeine causes increase bowel motility because, thinking about it, you would expect the opposite. Recall "fight or flight vs rest and digest". Fight or flight i mediated via adrenaline whilst rest and digest is a parasympathetic (cholinergic) function. Hence the gut is inhibited by adrenaline, whilst cholinergic agonists act as motility stimulants.

That's why it's actually a misnomer to say "I was so scared I shat myself" because when you are really scared (highly adrenalised) you can't. For exactly the same reason when 2 men stand directly next to each other at the urinals, they will usually take much longer to start peeing because they are subconsciously more stressed.

Chris

"I never forget a face, but in your case I'll make an exception"
 - Groucho Marx

[Ylide]

So why does my first cup of coffee every day provoke my, erm, morning constitutional?



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[chris]

I'm not sure that it does ! Perhaps merely getting up to make the coffee is sufficient to provoke a bowel movement ?

Chris

"I never forget a face, but in your case I'll make an exception"
 - Groucho Marx

[bezoar]

I read sometning about caffeine being a good laxative.  Also drinking it hot helps.

[Donnah]

I've read that large amounts of coffee can contribute to constipation.  The theory goes that coffee is a diuretic that removes enough water from the intestines to slow peristalsis.

Jay, I've also read that the body goes into an absortion cycle at night which is followed by an elimination cycle in the morning.  If I remember correctly that was from Dr. Deepak Chopra.

[Loffe]

Hi there, actually caffeine increases the rate at which contents of the stomach is emptied into the small intestine. That might account for why coffee jump starts your stomach in the morning. Concerning the subtle differences I would guess that it is due to different affinities for different adenosine receptors which methylxantines antagonise. The inhibitory effect on phospodiestereases is merely a contribution to their effects.